Light pipes are typically cylindrical, transparent structures through which light is channeled longitudinally by total internal reflection. Total internal reflection occurs when light is transmitted at a critical angle from one medium to another medium with a lower index of refraction. At the critical angle, light is reflected back into the medium of higher refractive index instead of being refracted by the change in media and traveling through the second medium. All or some of light transmitted through a light pipe may undergo total internal reflection. Light not internally reflected is emitted from the light pipe along the length of the light pipe.
Light pipes transmit light generated by a light source. The light source is usually contained in a lamp assembly to which the light pipe is fastened. A typical lamp assembly includes a housing that contains a light source such as a light emitting diode (LED), necessary electrical components to supply power to the light source, and a means for fastening the light pipe to the lamp assembly.
In many light pipe applications the space to accommodate the light pipe and associated lamp assembly is limited. Interior automobile lighting is an example of such an application. Therefore, a need exists to minimize the dimensions of lighting assemblies that include light pipes.
It is also desirable to maximize the light pipe output. Efforts to maximize output are typically directed to minimizing light degradation. Further improvements to maximize light pipe output are desirable, particularly for applications associated with limited space.
Providing a secure connection between the light pipe and lamp assembly is a further design consideration. Poor connections reduce reliability of the device. Because a light pipe typically has a smooth, cylindrical exterior, it may easily disconnect from a lamp assembly. Clamps, epoxies or other securing mechanisms require additional fabrication steps or components. Therefore, a need exists for a secure connection that is easily implemented without incurring added cost or time.